This invention relates to motor vehicle lift type tailgate control systems and more particularly to controlling the operation of the tailgate with respect to contacting an obstacle during opening and closing movements and also with respect to its final closing movement.
In motor vehicle bodies such as the van type having a lift type tailgate (also called liftgate) that is swung about a horizontal hinge axis at its upper edge to open and close a large rear access opening, it is desirable to have a power actuator for operating the tailgate to relieve a person of the required tailgate operating effort and also as a matter of convenience. Because the tailgate must be lifted upward to open as compared to a tailgate that is hinged about a vertical axis and thus has its weight supported by its hinges, the opening effort required for the former is relatively large because of its unsupported weight and could present a major effort for some people and particularly those with a physical disability. The weight of the tailgate can be offset with counterbalancing devices but a powered tailgate is preferred for convenience as well as serving the disabled. Various forms of powered actuators such as a motor powered linkage system, cable system and crank arm system could be adapted to operate such a tailgate. However, during such powered movement, the tailgate may unexpectedly encounter an obstacle in its path during both opening and closing movement and it is desirable to cease its powered movement in that event to prevent damage to the obstacle and/or the tailgate and its power actuator.
A powered tailgate system that has been proposed and includes a feature for stopping the tailgate movement in such an event is disclosed in co-pending U.S. patent application Ser. No. 08/292,662 filed Aug. 18, 1994 and assigned to the assignee of this invention. In this system, a powered actuator with a reversible DC motor and a worm gear driven crankarm, efficiently operates the tailgate through a roller and guide with gas spring assist. The motor current is monitored by a control circuit that interrupts the power to the actuator motor to stop the tailgate when the current exceeds a certain level as occurs when the tailgate encounters an obstacle. While this system has proven adequate, it has been found that certain further precautionary features with respect to the tailgate operation are desirable and that they can be accomplished in a very cost effective manner with this type of tailgate actuating mechanism.
The present invention, in addition to providing for very effective stoppage of the tailgate on encountering an obstacle, also provides for automatic stoppage of the tailgate at a partially closed position that is set to leave an opening that would not clamp an obstacle that could quite possibly be encountered such as a package left in the tailgate opening. In addition, an audible signal is provided to alert a person in proximity to the tailgate to the fact that it is closing and a different signal is provided to particularly alert the person operating the tailgate that it has automatically stopped at the partially closed position. This gives the person controlling the operation of the tailgate the opportunity to inspect for an obstacle as the operator is then required to repeat a tailgate closing command to complete its closure movement.
In the preferred embodiment of the invention, a latch mechanism is provided that is operable to latch the tailgate to the vehicle body when the tailgate is swung to a fully closed position and a solenoid is included in the latch mechanism that is operable on energization to unlatch the tailgate. A tailgate power actuator mechanism is provided that is operable to swing the tailgate to open and close the opening. And the tailgate power actuator mechanism includes a reversible electric motor that is operable on energization in an opening mode to swing the tailgate to a fully open position and is operable on energization in a closing mode to swing the tailgate to its fully closed position. An alarm device for alerting persons of tailgate closure operation is provided that is operable on energization in one mode to emit one kind of sound and on energization in another mode to emit another kind of sound indicating a different tailgate closing condition.
An electronic control circuit is provided for operating the solenoid latching mechanism, the actuator motor, and the alarm device. The control circuit utilizes a microprocessor operating under program control to respond to a user-initiated opening or closing signal to move the tailgate in the selected direction. The opening and closing signals are provided by a momentary switch mounted in the vehicle and/or on a remote key fob using wireless communication to signal a remote receiver linked to the microprocessor. In the control circuit, feedback information to the microprocessor indicative of tailgate position is provided by a potentiometer coupled with the actuator motor and the microprocessor is programmed to operate with this information to stop the tailgate at a wide open position, a predetermined partially closed position and a fully closed position. Obstruction detection is performed by the microprocessor using an obstruction detection circuit and additionally by monitoring the position signal input from the potentiometer to stop the tailgate on encountering an obstacle. Activation of the tailgate latching mechanism is accomplished under the control of the microprocessor using a solenoid drive circuit and warning sounds indicating tailgate closure operation are provided using an audio amplifier that drives a loudspeaker in accordance with audio data received from the microprocessor. The audio data is such that one kind of sound is emitted during tailgate closure to the partially closed position and then a different sound is emitted alerting the person controlling the tailgate that it has reached this position. The person controlling the tailgate operation is then required to command a second closing signal to fully close the tailgate and in the meantime has the opportunity to assure that there is no obstruction remaining in the way. The tailgate is automatically stopped as a precautionary measure at the partially closed position which may for example be set to leave a six inch opening to accommodate without contacting an obstacle such as a package containing a fragile object that has been allowed to remain in the tailgate opening.
It is therefore an object of the present invention to provide a new and improved power actuator system for a motor vehicle lift type tailgate.
Another object is to provide a power actuator system for a motor vehicle lift type tailgate arrangement wherein the tailgate is stopped automatically at a wide open position, at a closed position, at a partially closed position but only during closure movement, and on encountering an obstacle during both opening and closing movement.
Another object is to provide a power actuator system for a motor vehicle lift type tailgate wherein one form of sound signal is emitted as the tailgate is initially being closed, the tailgate is automatically stopped on encountering an obstacle and also at a predetermined partially closed position, a different sound signal is emitted at the latter occurrence, and the system must be resignaled to complete tailgate closure.
These and other objects, advantages and features of the present invention will become more apparent from the following description and accompanying drawings wherein: